[mk207]

Q. 23

[kimmey]

does anyone have a mark scheme for the exam style ques from the text book ?

[kimmey]

also does anyone have the june 2011 paper and mark scheme ?

[handsome7654]

(Original post by mk207)
Q. 23

The answer is D,
cuz if you equate mw^2r to Bqv,
according to the question, q=e and m=m obv,
Using v=wr we can cancel v on both sides.
So, mw=Be
then using w=2pi/t
we get 2pim/T = Be
rearrange that to make T the subject and there you go!

[soldiersixteen]

Could somebody explain to me the answer to Q2 June2010
http://idisk.me.com/mail.matt/Public...W-QP-JUN10.PDF

I thought i just had to use "ft=mv-mu" but with that i get 100 not 50.
And Q4 as well thanks
Thanks

[schizopear]

(Original post by handsome7654)
The answer is D,
cuz if you equate mw^2r to Bqv,
according to the question, q=e and m=m obv,
Using v=wr we can cancel v on both sides.
So, mw=Be
then using w=2pi/t
we get 2pim/T = Be
rearrange that to make T the subject and there you go!

that's what i did and i got D but my mark scheme says the answer is B...

[jones_wise]

(Original post by soldiersixteen)
Could somebody explain to me the answer to Q2 June2010
http://idisk.me.com/mail.matt/Public...W-QP-JUN10.PDF

I thought i just had to use "ft=mv-mu" but with that i get 100 not 50.
And Q4 as well thanks
Thanks

You do use the equation Ft = m(v-u)

Ft = Area = (5000*40)/2 = 100,000

100,000 = m(v-u)
100,000 = 2000(v-0)
50 = v

I'm not sure about Q4, sorry.

[jones_wise]

(Original post by schizopear)
that's what i did and i got D but my mark scheme says the answer is B...

I've got that question in a booklet made by my college, and the answer in their mark scheme is D. I agree with handsome7654's working, so it must just be a mistake in the mark scheme.

[schizopear]

(Original post by jones_wise)
I've got that question in a booklet made by my college, and the answer in their mark scheme is D. I agree with handsome7654's working, so it must just be a mistake in the mark scheme.

i thought (hoped!) it might be a mistake - thanks

[soldiersixteen]

How do you do this

The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from the +4 μC
charge to the point between the two charges, where the resultant electric potential is zero?
A) 24mm
B) 40mm
C) 80mm
D) 96mm

Thanks

[kimmey]

(Original post by soldiersixteen)
How do you do this

The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from the +4 μC
charge to the point between the two charges, where the resultant electric potential is zero?
A) 24mm
B) 40mm
C) 80mm
D) 96mm

Thanks

you use the electric potential formula

V=Q/4piepsilon0 x r but the 4piepsilon0 cancels for both so jus ignore it

so for the 4uC you do V=4uC/120 and for the -16uC you do V=-16uC/120-x

equate them and solve for x you should get 24mm

[soldiersixteen]

(Original post by kimmey)
you use the electric potential formula

V=Q/4piepsilon0 x r but the 4piepsilon0 cancels for both so jus ignore it

so for the 4uC you do V=4uC/120 and for the -16uC you do V=-16uC/120-x

equate them and solve for x you should get 24mm

Thanks.
When i equate them, I get
480u-4ux= -1920u
-4ux=-2400u
x=600

where am i messing up?

[handsome7654]

(Original post by soldiersixteen)
Thanks.
When i equate them, I get
480u-4ux= -1920u
-4ux=-2400u
x=600

where am i messing up?

Do it like this;
Cuz the sum of the potentials at a distance x away from 4uC is 0, you get
+4u/4piepsilon0(x) - 6u/4piepsilon0(20-x) = 0, then add 6u/4piepsilon0(12-x) to both sides,
4u/x = 6u/120-x (the 4piepsilon0 bit cancels), then multiply by (120-x)
480u - 4ux = 16ux
so x = 480u/20u = 24mm!

[savage903]

(Original post by mk207)
Q. 23

Hi I got the answer of D, is it possible for you to upload a markscheme for these questions if yuo have one? Thanks

[mk207]

(Original post by savage903)
Hi I got the answer of D, is it possible for you to upload a markscheme for these questions if yuo have one? Thanks

there you go

[maths134]

I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.

[mk207]

can you put them up ???

[AreebWithaHat]

(Original post by maths134)
I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.

could you PM them please to me?

[handsome7654]

(Original post by maths134)
I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.

Can I ask how you got access to all those past papers? If there is a website for them, can u give me the link plzz?? Really need some practice cuz iv only been getting C/Ds on my practice papers!!

[maths134]

If you guys want to spend a day working it out, you welcome to...